1. Field of the Invention
This invention relates generally to aircraft capable of flight at supersonic Mach numbers and, more particularly, to aircraft of the type described which utilize favorable aerodynamic interference effects which reduce drag and increase lift to provide efficient extended supersonic cruise. Such aircraft have both military and commercial utility.
2. Background of the Invention
Existing supersonic aircraft typically employ thin, highly swept wings and slender bodies which utilize an integrated propulsion system in an attempt to produce aerodynamically efficient designs. However, with such conventional designs, the lift to drag ratio decreases significantly at higher Mach numbers. This is due, in part, to decreased lifting effectiveness of the wing surfaces and increased wave drag at such velocities.
It has long been theorized that these difficulties could be alleviated if such aircraft were able, in some manner, to utilize mutual interactions of the flow fields generated at higher Mach numbers to augment lift and reduce drag. Initially it was believed this could be accomplished by reacting shock waves against existing wing designs to produce an upward or lifting force component. To create the necessary shock wave(s) at the appropriate location(s), it was suggested that volume elements, such as non-flight functional wedges or semi-cones, be positioned on the lower surface of the wing. This design has not proven to be practical because of excessive drag produced by such bodies. Another design that offered some promise, at least in theory, was the semi-ring wing, which utilized a full body or fuselage suspended beneath a wing formed as a semi-annulus with the body at its diametrical center. Although this arrangement is capable of capturing shock disturbances beneath the wing, the structural requirements of the member needed to connect the large body to the wing caused a significant drag increase which substantially offset drag reduction of the favorable interference effects. This fact and associated structurual problems of the connecting member proved this design impractical. Other designs involving a wing-suspended fuselage suffer similar disadvantages. Another disadvantage occurs because of the size of the fuselage body generally associated with such designs. That is, the fuselage-wing separation distance necessary for optimum wave drag cancellation effects becomes too large to permit optimum multiple wave reflections. Since multiple reflections are a significant factor in the augmentation of lift and wave drag cancellation is a significiant factor in drag reduction, benefits of these designs are inherently limited. Various other proposed designs such as the wave rider, the Buseman biplane and the Nonweiler wing, while offering theoretical promise, have produced no practical aircraft.
It is, accordingly, an object of the present invention to provide a practical, favorable interference aircraft that overcomes these and other disadvantages and limitations of the prior art.
It is another object of the invention to provide a practical, favorable interference aircraft that requires no single function elements to produce the necessary pressure fields.
It is a further object of the invention to provide a practical, favorable interference aircraft that utilizes the pressure fields generated by wing-suspended engine nacelles reacting against parabolically curved wings to augment lift and reduce drag for efficient, extended, supersonic cruise.
It is another object of the invention to produce a practical, favorable interference aircraft that utilizes wing mounted nacelles designed to optimize pressure field generation.
It is still another object of the invention to provide a practical, favorable interference aircraft that utilizes a wing plan form which reduces negative pressure effects and associated drag.